Robots are fast, automatic machines which can be equipped with various tools. The fundamental advantage of such processing equipment is its great flexibility. But this can only be achieved if tools can be mounted, which guarantee high processing speeds. Otherwise, a processing station equipped with robots is too slow when compared with a conventional solution; or, if many robots are operated at once, it is not profitable. The trend is therefore toward very fast robots with correspondingly fast tools. This is very demanding of the tools with respect to endurance and thermal capacity. An example serves to illustrate: to cast a motor vehicle radiator, a very complexly molded part, either an expensive press tool or a less costly robot can be used. Due to the slow working speed of the robot that solution is not economical. Since, on the other hand, the amortization time of the expensive press tool is too long, such parts are debured by expensive manual labor.
The processing speed of the robot can be increased, if the area to be worked is cooled. This is particularly valid for devices for grinding, milling, drilling, and polishing. A quick and intensive cooling can be achieved with cryogenic refrigerants, for example with liquid nitrogen. Due to the finite thermal conductivity of the materials to be processed, a lead time for the cooling of the area to be processed is to be strived for. Simultaneous cooling and processing would not allow the processing speed to increase to the maximum possible. There exist definite relationships between the penetration depth of the cold front, the rate of feed of the tool and the distance between the cooling zone and the work zone, which can be determined though testing. Therefore, an exact proportioning and delay-free admission with the refrigerant is an imperative condition for the optimal use of a robot whose work area is to be cooled with a cryogenic refrigerant. In addition, the refrigerant must be transported to the constantly moving robot joint with as little loss as possible.
Considerable practical difficulties oppose the desirable use of a cryogenic refrigerant, particularly liquid nitrogen. In order to avoid unwanted gas blockages in the transport conduit to the processing point of the robot-arm, the flexible conduit must be well insulated. An effective insulation, for example a double-walled corrugated hose with multiple-layer vacuum insulation or a hose insulated with mineral materials, would, however, be so inflexible that it could either not be installed on the robot at all, or its endurance would be insufficient. The demands for optimal insulation and higher flexibility as well as greater endurance are therefore in conflict.